on this saturday night, swinging away. on the trail today both campaigns barnstorming through swing states, unleashing some of the sharpest attacks we've seen yet. powerless along the gulf coast as remnants of isaac move through the drought-stricken heartland. why heavy rain turns out to be the last thing they need right now. at risk. thousands of visitors to one of the country's most popular tourist spots, warned they may have been exposed to a deadly virus. record highs. gas prices soaring, more expensive on a labor day weekend than ever before. field of dreams with an eye-popping price tag. one high school taking friday

night lights to the extreme. captions paid for by nbc-universal television good evening. they are the traditional sign posts of summer's last gasp, labor day, back to school shopping, the start of college football and in this election year, the start of the two toughest months in politics. this half-time weekend between the republican and democratic conventions has given both mitt romney and president obama plenty to say today. romney fresh off his nomination, trumpeting the anti obama themes in this gop convention. the president on the road to charlotte today reminding voters of what republicans didn't talk about. in a moment we'll check in with ron mott and the romney campaign. we'll begin with kristen welker on with the president in sioux

city iowa. >> reporter: good evening, lester. with the democratic national convention just a few days away, president obama is working to build momentum in key battleground states like right here in iowa where he's making his seventh visit so far this year. >> hello iowa! >> reporter: president obama kicking off his road to charlotte campaign in iowa, the state that first launched his presidency four years ago. >> it was you, iowa, who kept us going when the pundits were writing us off. and it will be you, iowa, who choose the path we take from here. >> reporter: polls show a tight race here as some white working class voters who gave him an edge four years ago aren't so sure because of the economy. >> iowa is important, and i think other states will look at iowa and say, if they're turning away from barack obama, that is a harbinger for the rest of the country. >> reporter: today the president reached out to those disaffected voters by slamming mitt romney's

convention speech. >> it was a rerun. we had seen it before. you might as well have wachtche it on a black and white tv. he did not offer a single new idea, just retreads of the same old policy that is have been taking it to the middle class for years. >> reporter: he took romney to task for not mentioning the troops in afghanistan. >> governor romney had nothing to say about afghanistan last week, let alone offer a plan for the 33,000 troops who will have come home from the war by the end of this month. >> reporter: heading into charlotte, political analysts say president obama will need to counter romney's message that the hope and change candidate didn't dlifer. >> obama has to make two cases, one, that things were really bad before and he made them better and two, in the second term, he'll make them better than romney would do. >> reporter: a potentially sharp task with sharply divided

electorate. i was with nbc news traveling with the president in sioux city, iowa. >> reporter: this is ron mott with the romney campaign. today mitt romney and paul ryan campaigned separately in the buckeye state, both greeted by enthusiastic crowds. mr. romney appeared with senator rob portman and house speaker john boehner in cincinnati. >> one of the promises he made was he was going to create more jobs. today 23 million people are out of work, stopped looking for work or underemployed. let me tell you, if you have a coach that's zero and 23 million, you say it's time to get a new coach. >> reporter: his running mate, paul ryan, meanwhile carried the sports theme further in ohio, playing corn hole. at the season opening football game between miami university of ohio and ohio state. >> you're in ryan country now.

it's his speech at the republican national convention, especially his criticism of the president over a shaut tered gm plant in janesville, wisconsin that continues to sizzle. >> it's locked up and empty to this day. that's how it is in so many towns where the recovery that was promised is nowhere in sight. >> reporter: democrats in the obama campaign fired back, noted the plant was slated foreclosure before mr. obama won the 2011 election. >> blaming the president for something that, a, happened under president burn and b, was a final decision made by the auto industry, that's really beyond the pale. >> reporter: back on the trail, the republican ticket reunited late today in florida. another battleground. >> we're tired of being told that someone else is responsible for our difficulties. it's time for us to take responsibility for the course of america to get us back on track. >> reporter: from here governor romney will take the next couple days off.

meantime paul ryan will campaign on monday, labor day monday in north carolina. that's, of course, where the democrats will hold their convention next week. lester. >> ron mott in florida. a program note, our prime time coverage of the democratic national convention starts tuesday night at 10:00 eastern, 7:00 pacific here on nbc. to another big power we've been covering this week. what was once hurricane isaac and the damage it did along the gulf coast. tonight as the cleanup continues, hundreds of thousands of people are still without power and patience is beginning to wear thin. nbc's gabe gutierrez joins us once again from new orleans. gabe, good evening. >> reporter: there's late word tonight that st. tammany parish is evacuating 1200 homes over concerns that a boat lock on a river could fail. all this as crews scramble to restore power to the gulf coast. in parts of louisiana, the waters are receding, but so is the patience.

>> this is the first time i've seen trucks in this neighborhood. >> reporter: thousands of line crews are on the move as the gulf coast struggles to recover from isaac, the slow-moving hurricane knocked out power to more than a million customers in louisiana, mississippi and arkansas. tonight almost 400,000 homes and businesses are still in the dark. the vast majority in louisiana. outside new orleans, beth goddard was desperate for shade after losing power four days ago. >> it's 95 degrees inside my house. so you're really not sleeping, not eating a whole lot. >> reporter: this family-owned grocery store just got power this afternoon. >> how much inventory do you think you lost? we think we lost somewhere between five and $700,000 worth of total inventory. >> reporter: workers are restocking shelves after throwing so much away. >> we didn't see any entergy trucks, i don't know where the phantom electricians are. they weren't out here trying to get the people back up.

>> reporter: frustration is so high that the president of jefferson parish is calling for a state investigation. >> i wouldn't be as upset and infuriated if they were out doing the work. there's no presence on the street. >> reporter: entergy says crews from around the country are working as fast as possible. >> this was a slow-moving category 1 storm that sat over the city for almost two days. this was more of a wind event. >> reporter: in plaquemines parish, power or lack of it is not the most pressing concern. some still can't even see their homes. others like rachel are thankful for what they salvaged. >> i saved everything on my second floor and i saved my little boy's tortoise. all he wanted was his russian tortoise. that's all he wanted. >> reporter: the electric company now expects about 75% of new orleans to have power by monday. lester, the army corps of engineers now says that it will check whether new orleans upgraded levee system

contributed to more flooding outside the city. >> gabe gutierrez in new orleans tonight. thanks. tonight the remnants of isaac are moving to the midwest dumping heavy rain in some of the most draut stricken areas of the country. unfortunately it's finally raining at one of the worst possible times. weather channel meteorologist julie martin is in kankakee, south of chicago to tell us more about that. >> reporter: good evening lester. we're getting a temporary break in the rain on this last weekend of summer. most midwest farmers are getting what they've wanted since the growing season began and that is just that. however, with the good also comes the bad in the form of severe weather. first, though, let's start with the good. generally we're looking at two to four inches across the midwest in states like illinois, indiana and ohio, just drought-stricken states. indianapolis, by the way, has already picked up about three inches today. in central illinois -- sorry -- springfield has already picked up about two inches.

with that also comes some very unstable air left behind by isaac. we are looking at a severe weather threat. three tornadoes already reported today, lester. more threats will exist tomorrow, just a little further eastward. >> julie martin, thank you. on this holiday weekend, a growing health al hert tonight at one of the most popular tourist destinations in the country. yosemite national park in california. health officials say at least two people have died after being exposed to a mouse-borne virus there. they're warning thousands more who have overnighted at the park that they might be at risk. we get more from nbc's miguel almaguer. >> reporter: they come from around the world for the grandeur, to see the soaring granite dome of half dome, the lash canopy of the trees and acre after acre of unmatched raw natural beauty. this holiday weekend, an estimated 75,000 people will visit yosemite national park. but this pristine reserve comes

with a warning. >> there's information about the hanta virus. >> reporter: a rare rodent-borne disease has been found in curry village, a popular campsite. the centers for disease control confirms six cases in yosemite so far, two fatal. the cdc says 10,000 campers may have been exposed to the deadly virus, spread primarily through deer mice. >> initial symptoms may be nonspecific, similar to the flu such as muscle aches, pains, fever, chills, headache. >> we really upped our education in the outreach in the last two weeks. >> reporter: with 91 cabins temporarily shut down, the park has been flooded with some 2,000 calls from concerned tourists. >> we have had some cancellations, especially here at curry village. >> reporter: attendance has dipped, the hanta virus scare hasn't kept the large crowds away. >> i've been coming up here all

my life. nobody is going to stop me from coming back, not even a little mouse. >> reporter: one of the world's natural wonders still a draw as health officials hope to contain a rare and worrisome disease. miguel almaguer, nbc news, los angeles. tonight investigators are combing through wreckage after a deadly crash at an air show in iowa. it happened at the quad cities air show when a training jet flying in formation crashed into a field and burst into flames, killing the pilot. no one in the crowd was hurt. at penn state today there was a moment of silence before the first football game of the new season. the crowd honoring the victims of child sex abuse. it was the first start to a penn state season without joe paterno on the sidelines since 1949. his widow, sue pa certain know did attend the game. as "nbc nightly news" continues, sticker shock this labor day weekend as gas prices reach record high. so what's to come? later they say everything is

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for relief from tough headaches. we're back with what seems to be an annual rite of summer travel. about the time the three-day weekend comes around, gas prices suddenly go up. in this case we haven't seen gas prices this high and they took a big jump this week. nbc owes tom costello explains why. >> reporter: the last great escape of summer 2012.

if your mode of transportation involves tires, it turns out a labor day getaway has never been more expensive. gas price haves jumped ten cents in a week, 30 cents in a month. hurricane isaac gets much of the blame as it took aim at louisiana, oil rigs, refineries, even a critical pipeline all shut down. while they escaped unharmed, the downtime pushed prices higher. add in a ruptured pipeline in wisconsin, refinery problems in the midwest, a fire at a california refinery last month and an expensive summer blend, it all spells higher prices. >> americans are faced with the highest prices we've ever seen on labor day weekend across the united states. >> reporter: look at los angeles. the average is now $4.16 a gallon. >> of course the motor home is going to be sitting home this weekend because it's going to be way too much money to fill it up. >> reporter: gasbuddy.com's heat map shows the least expensive states from green to red, 3.78

in massachusetts, $3.97 in new york. and $4.15 in chicago and illinois. in chicago nearly $4.34. >> i have to make changes with how i buy food, how i do my bills. >> reporter: this is interesting. aaa cac lates if you're driving from atlanta to kansas city in a 2008 toyota van, you'll pay about $192348 fuel. same vehicle from new york to chicago, about $200. from spokane to palm springs about $358 in fuel. the good news, gas prices aren't expected to stay this high. as refineries start switching to a less expensive winter blend, their inventories will come back up. gas prices, it's hoped, will start to go back down. >> between thanksgiving and christmas, the national average may drop to the mid $3.00 range. some areas could drop even lower than that. >> reporter: in the short term, getting around is going to cost

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more than half a century after the infamous morning sickness drug caused birth defects in thousands of babies. the german pharmaceutical company behind that mid lied is saying it's sorry and unveiling a statue to memorialize the victims. some say too little, too late. the drug was sold to pregnant women in 46 countries in the late '50s and early '60s though not here in the u.s. before being pulled in 1961. the fear of shark is keeping families off the beach this holiday weekend in cape code. beaches were closed undefinitely after several sightings the last couple weeks including great whites near the coast. the country's oldest zoo has a unique attempt to make things more wild. the latest phase of the program at the philadelphia zoo has just opened. the zoo plans to spend another $2 million to expand it.

a visit tonight with nbc's michelle franzen. >> so right now we're going to do a feeding. we've come up with this handy contraption. >> reporter: zookeeper samantha nester feeds her your orangutans this way because up there is where they like to hang out. >> reporter: the idea of creating this note work is coming out of our interest in creating a great experience for animals here. >> reporter: and this is just the beginning. over the next eight years, organizers will build more pathways across the zoo's 42 acres. the first trail unveiled last year had an immediate and positive effect on the small pry mates. they were stimulated by the extra space and new sights and smells, happy to be in an environment that more closely resembles the wild. last week the zoo opened a new trail for its great apes. >> the minute we opened the door, they came out and were checking it out. they seem to embrace it.

they're enjoying it quite a bit. >> reporter: the animals are not the only ones benefitting from the change. >> it's really, really fun to watch the visitors. they understand on any given day they might see a different animal out there and they might see the animals doing very different things. >> it is very fun to see these animals swing around. >> i like the baby, and they're so cute. >> reporter: as other zoos take notice and think about a turn to the wild, it's possible that one day we'll find our favorite animals wandering the grounds, exploring just like us. michelle franzen, nbc news. it won't happen again for another three years. last night folks around the world were treated to beautiful blue moon, the second full moon in the month of august. lots of professional and amateur photographers alike capturing images of the last blue moon until 2015. by popular demand, the white house today released the recipes for two home made beers being brewed at 1600 pennsylvania

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school unveiled a $60 million stadium for high school football. while that figure is raising some eyebrows, the folks there say it's worth every penny. we get the story now from nbc's charles hadlock. >> reporter: in texas where football is almost a religion, the friday night lights are shining bright her the dallas suburb of allen. >> it's great. >> it's awesome. >> reporter: the school district last night christened its new $60 million football palace, home of the allen eagles. >> it's exciting. it's fun to play with my teammates. >> reporter: the stadium seats 18,000, nearly 22,000 showed up for opening night including former dallas cowboy emmitt smith. >> all i can say is it's pretty awesome. >> reporter: there's a huge scoreboard with instant replay and a plush press box sitting atop a touring upper deck, not to mention a weight room that's 50 yards long and concession stands on every corner. >> it's excessive but i like it.

>> it's like going from an out house to a real bathroom for real. >> reporter: the new stadium replaces an aging one built 30 years ago when allen had fewer than 8,000 residents. 87,000 people live here now and they want to see their kids play football in grand style. >> reporter: nearly 64% of allen voters approved the bond election for the money to this build this stadium. even though they'll never sell enough $10 tickets to recoup their money, fans say there's something more at stake here. >> it's an investment in the future of the kids and in the future of the town. >> reporter: and it's not just the players who win. students from the high school run the giant scoreboard, operate cameras on the sidelines, sell at the concession stands, and others perform in a 700-member band. >> when you can engage a thousand kids on a friday night, a lot of proud parents, 3,000, 4,000 proud parents on top of that, if nobody showed up, you'd

have an incredible experience. >> the school pride that comes with something like this isn't something you can pay for. >> reporter: that, fans say, is worth every dollar spent. >> whoo! >> reporter: charles hadlock, nbc news, charles, texas. that's "nbc nightly news" this saturday, i'll see you right back here. good night.